I really don't think that GOG would refuse it so if it goes on sale DRM-Free on Humble but not here it's probably a question of exclusivity which, should it be confirmed somehow, would be too bad.
As one other post said, we can always go the Humble road but, except for the bundles (and even for those it's becoming rare), I try to keep away from them because I try to have all my games in one place and the user account is awful.
I read a lot of complaints about Galaxy and, undoubtly, there is still work to be done and the update pace feels quite slow but compared to managing your game updates on your Humble account it's heaven on earth. and for a game like Grim Dawn which has the potential to have regular balancing update, it's a recipe for headaches.
So I'll wait for it to come here or miss it (which would be too bad because Titan Quest it the best Diablo contender I played - Torchlight coming 3rd with Dungeon Siege).